全文获取类型
收费全文 | 17519篇 |
免费 | 1303篇 |
国内免费 | 6篇 |
出版年
2023年 | 152篇 |
2022年 | 158篇 |
2021年 | 480篇 |
2020年 | 383篇 |
2019年 | 442篇 |
2018年 | 636篇 |
2017年 | 565篇 |
2016年 | 724篇 |
2015年 | 973篇 |
2014年 | 1053篇 |
2013年 | 1392篇 |
2012年 | 1416篇 |
2011年 | 1397篇 |
2010年 | 955篇 |
2009年 | 770篇 |
2008年 | 890篇 |
2007年 | 862篇 |
2006年 | 756篇 |
2005年 | 619篇 |
2004年 | 541篇 |
2003年 | 481篇 |
2002年 | 435篇 |
2001年 | 321篇 |
2000年 | 296篇 |
1999年 | 245篇 |
1998年 | 134篇 |
1997年 | 94篇 |
1996年 | 83篇 |
1995年 | 92篇 |
1994年 | 81篇 |
1993年 | 72篇 |
1992年 | 137篇 |
1991年 | 122篇 |
1990年 | 94篇 |
1989年 | 86篇 |
1988年 | 94篇 |
1987年 | 73篇 |
1986年 | 70篇 |
1985年 | 57篇 |
1984年 | 62篇 |
1983年 | 44篇 |
1982年 | 40篇 |
1981年 | 36篇 |
1980年 | 35篇 |
1979年 | 45篇 |
1978年 | 34篇 |
1977年 | 22篇 |
1976年 | 22篇 |
1975年 | 31篇 |
1973年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
A.C. Gonçalves T.D. Matos H.R. Simões-Teixeira M. Pimenta Machado M. Simão Ó.P. Dias M. Andrea G. Fialho H. Caria 《Gene》2014
Low-frequency sensorineural hearing loss (LFSNHL) is an unusual type of HL in which frequencies at 2000 Hz and below are predominantly affected. Most of the families with LFSNHL carry missense mutations in WFS1 gene, coding for wolframin. 相似文献
3.
ENRIQUE JHONATAN ROMO-MARTÍNEZ GABRIELA MARTÍNEZ-CORTÉS REYNA LUCÍA BARAJAS-TORRES RODRIGO RUBI-CASTELLANOS MARÍA TERESA MAGAÑA-TORRES HÉCTOR RANGEL-VILLALOBOS JUAN RAMÓN GONZÁLEZ-GARCÍA 《Journal of genetics》2012,91(3):297-302
Morphological variation of the Y chromosome has been observed in different populations. This variation is mostly related to the heteromorphic Yq12 band, which is composed of a variable block of constitutive heterochromatin. The Yqh+ heteromorphism has a worldwide frequency of 2.85% and is considered clinically innocuous. The aim of this study was to identify the ancestry of the Yqh+ heteromorphism present in individuals from western Mexico. For this purpose, 17 Y-chromosome single nucleotide polymorphisms were analysed by multiplex polymerase chain reaction and SNaPshot assays. In 28 Yqh+ males, only five haplogroups were observed; with a haplogroup diversity of 0.4841 ± 0.1094, which was less than that observed in a study of unselected Mexican mestizo population. Differences were specifically conferred by the high frequencies of haplogroups R1b1 and P*(xQ,R), and by the absence of the Amerindian haplogroup Q (Q*(xQ1a3a) plus Q1a3a) from the Yqh+ group. This study suggests a post-1492 incorporation for Yqh+ chromosomes into the Mexican northwestern population. 相似文献
4.
5.
Thiago B. Kirsten Marcella C. Galv?o Thiago M. Reis-Silva Nicolle Queiroz-Hazarbassanov Maria M. Bernardi 《PloS one》2015,10(3)
Sickness behavior is considered part of the specific beneficial adaptive behavioral and neuroimmune changes that occur in individuals in response to infectious/inflammatory processes. However, in dangerous and stressful situations, sickness behavior should be momentarily abrogated to prioritize survival behaviors, such as fight or flight. Taking this assumption into account, we experimentally induced sickness behavior in rats using lipopolysaccharides (LPS), an endotoxin that mimics infection by gram-negative bacteria, and then exposed these rats to a restraint stress challenge. Zinc has been shown to play a regulatory role in the immune and nervous systems. Therefore, the objective of this study was to examine the effects of zinc treatment on the sickness response of stress-challenged rats. We evaluated 22-kHz ultrasonic vocalizations, open-field behavior, tumor necrosis factor α (TNF-α), corticosterone, and brain-derived neurotrophic factor (BDNF) plasma levels. LPS administration induced sickness behavior in rats compared to controls, i.e., decreases in the distance traveled, average velocity, rearing frequency, self-grooming, and number of vocalizations, as well as an increase in the plasma levels of TNF-α, compared with controls after a stressor challenge. LPS also decreased BDNF expression but did not influence anxiety parameters. Zinc treatment was able to prevent sickness behavior in LPS-exposed rats after the stress challenge, restoring exploratory/motor behaviors, communication, and TNF-α levels similar to those of the control group. Thus, zinc treatment appears to be beneficial for sick animals when they are facing risky/stressful situations. 相似文献
6.
The accumulation of proline (Pro) in plants exposed to biotic/abiotic stress is a well-documented and conserved response in most vegetal species. Stress conditions induce the overproduction of reactive oxygen species which can lead to cellular damage. In vitro assays have shown that enzyme inactivation by hydroxyl radicals (·OH) can be avoided in presence of Pro, suggesting that this amino acid could act as an ·OH scavenger. We applied Density Functional Theory coupled with a polarizable continuum model to elucidate how Pro reacts with ·OH. In this work we suggest that Pro reacts favourably with ·OH by H–abstraction on the amine group. This reaction produces the spontaneous decarboxylation of Pro leading to the formation of pyrrolidin-1-yl. In turn, pyrrolidin-1-yl can easily be converted to Δ1-pyrroline, the substrate of the enzyme Δ1-pyrroline dehydrogenase, which produces γ-aminobutyric acid (GABA). GABA and Pro are frequently accumulated in stressed plants and several protective roles have been assigned to these molecules. Thereby we present an alternative non-enzymatic way to synthetize GABA under oxidative stress. Finally this work sheds light on a new beneficial role of Pro accumulation in the maintenance of photosynthetic activity. 相似文献
7.
In a pot experiment, burning or clipping ofTrifolium pratense plants colonized by the vesiculararbuscular mycorrhizal (VAM) fungusAcaulospora scrobiculata increased the number of spores in the substrate and the abundance of vesicles. The length of external mycelium and inoculum potential increased with clipping, but decreased with plant burning. Results suggest that the loss of photosynthesising tissue does not explain the effect of burning on VAM propagule activity. ei]R O D Dixon 相似文献
8.
9.
10.
Joana Darc Souza Chaves Jaqueline Lopes Damasceno Marcela Cristina Ferreira Paula Pollyanna Francielli de Oliveira Gustavo Chevitarese Azevedo Renato Camargo Matos Maria Cristina S. Lourenço Denise Crispim Tavares Heveline Silva Ana Paula Soares Fontes Mauro Vieira de Almeida 《Biometals》2015,28(5):845-860